Honda believes its step forward in competitiveness in the Mexican Grand Prix was due to altitude rather than major gains from its power unit performance.

With Honda not expecting to be competitive at the Autodromo Hermanos Rodriguez, it took new power units for both McLarens in order to have a better chance of scoring strongly in the final two races in Brazil and Abu Dhabi. However, Fernando Alonso was quick in qualifying and recovered from a lowly grid position to finish tenth in the race, and Honda's head of F1 project Yusuke Hasegawa highlighted the altitude as one reason for the pace.

"We were much better than we expected, which was good, but we're also a little bit disappointed because from that race situation we could have aimed for seventh or eighth place," Hasegawa told RACER. "But of course we have to be satisfied with the result because we started from the back of the grid.

"So we think that our engine performance at high altitude is not much worse than at lower levels. So everybody should lose some power at altitude, but our level of power loss was not as big as the other manufacturers I don't think. So that's why we were competitive."

Asked about the qualifying performance shown by Alonso – who was fifth quickest in Q1 – Hasegawa replied: "It's obvious that we could have got into Q3.

"Our Q1 time with Fernando was enough for ninth in Q3 and we could have aimed for eighth or seventh, but we we knew we were going to start from the back of the grid so there was no point in trying as we could save some tires."

Despite the unique aspect of the altitude, Hasegawa is still confident the gains shown by the spec 3.8 power unit will see Honda remaining competitive in the final two races.

"Yes it has encouraged us, but Mexico is a very special circumstance and there's some level of engine power reduction. But still it is encouraging for us."

The biggest negative of the Mexico weekend was a power unit problem for Stoffel Vandoorne after his first installation lap in Friday practice, which led Honda to revert to an old engine for the rest of the weekend. However, Hasegawa says it turned out to be a small issue that will allow Vandoorne to re-use the upgraded power unit at Interlagos.

"The fuel pump has some sensors, and it's just a pin. So there was a pin issue, we think it was a missed connection, so we can just fix that and it will be fine to use in the last two races."